This invention relates to a cork friction material and a power controlling apparatus using such a friction material.
Cork is favorably used as friction material for various machine parts such as clutch facing in a motor control device or a power transmission apparatus in an electric-powered sewing machine, etc., for the reasons that cork has an optimal coefficient of friction for use as such friction material and that it substantially prevents creaky noise or odious smell from being produced by the friction surface in operation of the machine. However, there is a problem in the service life of cork because of its poor wear resistance. As an attempt for realizing longer life, Japanese Patent Appln. Kokai (Laid-Open) No. 4940/79 proposes coating of cork with a lubricating oil containing a solid lubricant. This cork friction material, however, is still unsatisfactory in life and further improvements are desired.